Analysis of Chromosomal Aberrations and DNA Mutations in Bone Marrow Mesenchymal Stroma Cells from Patients with Myelodysplastic Syndrome Amd Acute Myeloid Leukemia

Introduction: The biology of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) is not well understood. In MDS, ineffective hematopoiesis may result from disturbed interactions between hematopoietic cells (HC) and the hematopoietic microenvironment. Bone marrow mesenchymal stroma cells (BMSC) are key components of the hematopoietic microenvironment. BMSC from patients with hematological disorders display functional and quantitative alterations. However, the question whether BMSC in MDS/AML have cytogenetic abnormalities is discussed controversially.

Methods: In the present study, we have collected BMSC from 51 MDS and 42 AML patients at the time of initial diagnosis. Chromosome preparation was performed after cell culture for 30 days and analyzed by conventional cytogenetic (G-banding) and by different types of FISH-techniques. Furthermore, FLT3 and NPM1 mutation analysis was performed in HC and BMSC. As a control we have studied BMSC from 25 healthy individuals.

Results: Cytogenetic analysis of BMSC was successfully performed in 90 of the 93 cases. Clonal structural chromosomal aberrations, including t(1;7), t(1;10), t(1;2), t(7;9), i(1q), inv(X), del(7q), del(13q), del(17p), and others, were detectable in BMSC of 15% of patients. All cytogenetic markers were confirmed by FISH with specific probes and M-FISH. Interestingly, cytogenetic markers in BMSC differed from the aberrations in HC from the same individual. We have found cytogenetic abnormalities in BMSC from patients presenting with cytogenetic alterations in their HC as well as from those with normal karyotype. In BMSC we could not detect specific mutations of NPM1 and FLT3 (ITD and TKD), independent from the mutation status of HC. For control analysis, BMSC cultures from 25 healthy donors were prepared under the same conditions (time of culture, number and frequency of passages). BMSC from healthy donors did show normal diploid karyotypes and absence of DNA-mutations of NPM1 and FLT3.

Conclusions: Our data indicate that BMSC from MDS and AML patients are characterized by genetic instability. Lack of aberrations as detected in HC and appearance of novel clonal rearrangements in BMSC may suggest enhanced genetic susceptibility and potential involvement of BMSC in the pathogenesis of MDS and AML.